Accepted Manuscript

Hydrothermal fluid evolution and metal transport in the Kiruna District, Swe‐

den: Contrasting metal behaviour in aqueous and aqueous-carbonic brines

M.P. Smith, S.A. Gleeson, B.W.D. Yardley

PII: S0016-7037(12)00591-1

DOI: http://dx.doi.org/10.1016/j.gca.2012.10.015

Reference: GCA 7960

To appear in: Geochimica et Cosmochimica Acta

Received Date: 27 April 2012

Accepted Date: 9 October 2012

Please cite this article as: Smith, M.P., Gleeson, S.A., Yardley, B.W.D., Hydrothermal fluid evolution and metal

transport in the Kiruna District, Sweden: Contrasting metal behaviour in aqueous and aqueous-carbonic brines,

Geochimica et Cosmochimica Acta (2012), doi: http://dx.doi.org/10.1016/j.gca.2012.10.015

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Hydrothermal fluid evolution and metal transport in the Kiruna District,

Sweden: Contrasting metal behaviour in aqueous and aqueous-carbonic brines.

M.P. Smith1*

, S.A. Gleeson2 and B.W.D. Yardley

3.

1. School of Environment and Technology, University of Brighton, Brighton, BN2

4GJ, U.K.

2. Department of Earth & Atmospheric Sciences, University of Alberta, Edmonton,

AB, T6G 2E3, Canada

3. School of Earth and Environment, University of Leeds, Leeds, LS2 9JT, U.K.

*Corresponding author:

Dr. Martin Smith,

School of Environment and Technology,

University of Brighton,

Lewes Road,

Brighton,

BN2 4GJ.

U.K.

e-mail: martin.smith@brighton.ac.uk

Tel.: (+44)(0)1273 642265

Abstract

Iron oxide-copper-gold (IOCG) deposits and Fe oxide-apatite deposits from

Norrbotten, Sweden, formed in similar settings, and in some cases IOCG

mineralisation overprinted Fe oxide-apatite mineralisation. Fluid inclusions in quartz

veins cutting Fe oxide-apatite deposits range in salinity from 33-37 wt. % NaCl eq.,

and those in IOCG-type deposits from 41-54 wt. % NaCl eq. Minimum trapping

conditions for these inclusions are ~200-300MPa and 200-300°C in the Fe oxide-

apatite bodies, and 250->300MPa and 300-500°C in the IOCG deposits. Deformed

Cu-Au deposits have similar early fluid characteristics, but contain complex

secondary fluid inclusion assemblages including halite saturated (20-30 wt. % NaCl

eq.), aqueous-carbonic (3-13 wt. % NaCl eq.; X(CO2) 0.17-0.29) and CO2-rich fluids.

The aqueous-carbonic and carbonic inclusions are consistent with aqueous-carbonic

fluid immiscibility at ~150MPa. A secondary population, with a high Ca-content

occurs in all deposit types.

The chemical composition of these inclusions has been determined by crush-

leach analysis and LA-ICPMS. Halogen contents indicate a range of salinity sources

with possible inputs from both magmatic and halite-dissolution brines. Element ratios

suggest the alkali content of the fluid exceeded the buffer capacity of the host rocks.

Iron and other transition metal contents correlate strongly with Cl concentrations, with

secondary controls on solubility from pH, redox and temperature. Copper and Ag

contents are higher in lower salinity aqueous-carbonic brines (up to 5000ppm Cu,

900ppm Ag) than in the most saline brines (up to 2297ppm Cu, 837ppm Ag). This

may reflect differences in metal source between deposit types, but is also consistent

with the complexation of Cu by bisulphide in the lower salinity fluids. Late stage

aqueous-carbonic fluid flux through the deformed deposits either introduced

additional copper to the deposits, remobilised pre-existing copper or both.

1. Introduction

Iron oxide–copper–gold deposits (IOCG) are a relatively recently defined class of

ore deposit, which are characterised by Cu-sulphide ± Au hydrothermal ores with

abundant magnetite or hematite. Their classification has been problematical since the

definition of the Fe oxide-Cu-Au (IOCG) class of deposits by Hitzman (1992).

Subsequent research has refined the definition (Hitzman, 2000; Williams et al., 2005;

Groves et al., 2010), and suggested the Fe oxide-apatite (Kiruna-type) deposits are a

separate, but related, type of ore deposit. A range of genetic models have also been

proposed for IOCG deposits that have included the involvement of basinal brines,

fluids interacted with meta-evaporites, surface derived brines (e.g. Barton and

Johnson, 1996; 2000) and magmatic fluids in ore formation. Evidence from different

deposits and districts supports the potential involvement of all these fluid sources in

producing deposits of similar characteristics (e.g. Williams et al., 2001; Kendrick et

al., 2007, 2008a, b; Gleeson and Smith, 2009). The key linking factor in all models is

the involvement of high salinity brines, which account for the high total masses of Fe

deposited and the prevalence of Na-rich alteration including the formation of regional

scapolite and albite. There is also good evidence for mixing of different fluids, and/or

for numerous generations of fluid circulation (Broman and Martinsson, 2000;

Wanhainen et al., 2003; Gleeson and Smith, 2009), including CO2-rich fluids either

during the main stage of ore deposition, or involved in post ore modification of the

deposits (e.g. Williams et al., 2001; Fu et al., 2003; Baker et al., 2008). In many

instances in IOCG deposits Cu-(Au) mineralisation post-dates Fe mineralisation, with

Cu minerals either in cross-cutting veins or in breccia matrices, and may be the result

of the circulation of different fluids through the same deposit with a significant time

difference between the mineralising events (e.g. Smith et al., 2009). However, despite

the complex interaction of primary fluid sources, fluid mixing, immiscibility and

multiple generations of overprint, studies so far that have targeted the chemistry of

individual fluid inclusions have found the highest concentrations of ore forming

elements, particularly Cu, in high temperature, hypersaline fluids of inferred to be of

either magmatic derivation (Baker et al., 2008), or non-magmatic brines(Bastrakov et

al., 2007). Even in deposits with primary fluids suggested to be of magmatic origin,

however, there is evidence for the subsequent interaction of evaporate-derived brines

(Baker et al., 2008).

In this study, we report on the characteristics of aqueous and aqueous-carbonic

fluid inclusions from quartz veins cutting Fe oxide-apatite mineralisation, and hosting

Cu mineralisation in IOCG deposits, from the Kiruna and Malmberget ore districts,

northern Sweden (Fig. 1) with the aims of examining the formation conditions of the

veins and ores and the transport and deposition processes of metals. The study used

crush leach and laser ablation Inductively Coupled Plasma Mass Spectrometry (LA-

ICPMS) analyses of fluid inclusion chemistry to give constraints on both the cation

and anion composition of fluids, and to allow discrimination between different

populations in mixed inclusion assemblages where crush leach techniques would

average the chemistry of different populations.

2. Background geology

The detailed geology and metallogeny of Norrbotten County, Sweden, have

been reviewed by Carlon (2000) and Bergman et al. (2001). Fe oxide-apatite and

IOCG type deposits are hosted in a Palaeoproterozoic sequence of metavolcanic and

metasedimentary rocks, that can be broadly divided into the Karelian Greenstone

Group (>1.9Ga) and the Svecofennian Porphyry Group (Fig. 1). The Greenstone

Group consists of dominantly tholeiitic to komatiitic volcanic rocks, and overlies

Archaean basement (Ekdhal, 1993). The Porphyry Group consists of andesitic

(Porphyrite Group) to syenitic and quartz-syenitic (Kiruna Porphyries) igneous rocks

and associated sediments (Martinsson, 1997). The Kiruna Porphyries host the

Kiirunavaara magnetite-apatite deposit, and may have acquired their syenitic

character by metasomatism, and the porphyry group has been identified as initially

consisting of a sequence of basalt, trachyandesite and rhyodacite-rhyoite (Martinsson

and Perdahl, 1995; Bergman e al., 2001). Storey et al. (2007) suggested a minimum

formation age for these units of ca. 2050Ma. These rocks are cut by the calc-alkaline

Haparanda and Perthite-Monzonite granitoid suites (1.9-1.8Ga; Skiöld, 1987),

followed by the Lina suite granitoids at around 1.79Ga. The country rocks underwent

metamorphism, peaking at upper greenschist to lower amphibolites facies conditions

from 1.9-1.8Ga (Skiöld, 1987). The rocks are affected by albitisation and

scapolitisation on the regional scale (Frietsch et al., 1997), which occurred at

~1903±8Ma (Smith et al., 2009). A number of large-scale shear systems cut the area,

including the Nautanen Deformation Zone (NDZ), a NNW-trending structure with

schistose or mylonitic rocks occurring in several high strain branches in a zone up to

3km wide (Martinsson and Wanhainen, 2004).

Samples for this study were taken from three groups of deposits and prospects;

late-stage quartz veins cutting Fe oxide-apatite deposits and associated alteration,

mineralization-related quartz veins from Cu-(Au) prospects hosted by the Greenstone

and Porphyry Groups, and mineralization-related quartz veins from the heavily

deformed metavolcanic rocks of the NDZ. The Fe oxide- apatite bodies

are typified by the Kiirunavaara-Luossavaara body, dominated by magnetite, and the

Per Geiger ores, with both hematite and magnetite (Geijer, 1910; Martinsson, 2004).

The formation of the Kiirunavaara-Luossavaara ores has been dated at 1880-1870Ma

(Romer et al., 1994; Smith et al., 2009), which is coeval with both the intrusion of the

Haparanda and Perthite-Monzonite suite granitoids, and peak metamorphic conditions

in the area (Bergstrom et al., 2001), although the ores underwent a second period of

metamorphism and possibly hydrothermal alteration at ~1800Ma (Romer et al., 1994;

Smith et al., 2009). Quartz veins cross-cut magnetite and/or hematite in these deposits

(Fig. 2A, B) and so cannot be directly linked to ore deposition. However, the quartz

veins also include actinolite, magnetite, hematite and titanite (Fig. 2A, B), and do not

show alteration haloes when cross-cutting oxide ore (there is no hematisation of

magnetite; Fig. 2C). We therefore argue that these veins represent the latest stage

fluid associated with the main stage of Fe oxide deposition, and hence have provide

some constraints on the transport of metals in these systems. Hematite-bearing veins

do occur, and are represented in this study by the late stage quartz vein sample from

Kirunavaara (KR2), and veins from the Nuktus deposit.

The IOCG deposits occur in both Greenstone Group and Porphyry Group

rocks affected by sodic , (including both scapolite and albite), potassic and carbonate

alteration (Martinsson, 2004). It is likely that IOCG mineralisation post-dated Fe

oxide-apatite mineralisation by 10-20Ma (Martinsson and Virkkunen, 2004; Smith et

al., 2009). In these deposits quartz veins host chalcopyrite and pyrite, and so the

deposition of quartz can be closely related to ore mineral deposition (Fig. 2D, E).

Quartz veins directly associated with Cu mineralisation were also taken from

sites associated with the NDZ, where shear-zone hosted mineralisation is associated

with the development of scapolite, tourmaline, sericite, K-feldspar, epidote and garnet

(Martinsson and Wanhainen, 2004). The samples come from both the Nautanen

prospect, and from the Ferrum vein hosted Cu-Au prospect on the margins of the

main deformation zone. An additional sample from the Aitik Cu-Au mine

(Wanhainen et al., 2003) was analysed for comparison with the Nautanen samples. It

has been suggested that primary mineralisation in the NDZ was formed at a similar

time to other mineralisation in the area (1870-1890Ma; Wanhainen and Martinsson,

2003; Wanhainen et al., 2005), although the Aitik deposit may represent a deformed

and metamorphosed porphyry-Cu system (Monro, 1988). The ore mineral assemblage

in both deposits is typified by pyrite, chalcopyrite, magnetite and pyrrhotite (Fig. 2F).

Both the Nautanen prospect and Aitik deposit were significantly modified, and ore

metals remobilised by subsequent deformation and metamorphic events associated

with the formation of the deformation zone, notably at ~1760Ma (Wanhainen et al.,

2005; Smith et al., 2009). Secondary fluid inclusions can be related to either

remobilisation of Cu or addition of Cu to the deposits as sulphides phases occur as

solid inclusions along secondary fluid inclusion trails (Wanhainen et al., 2003).

The settings and characteristics of individual samples are described in Table 1,

and additional descriptions of the same samples are given by Gleeson and Smith

(2009).

*3. Methods

3.1 Fluid inclusion microthermometry

Inclusions were classified as primary, pseudosecondary or secondary using the

criteria of Roedder (1984), and using their room temperature phase assemblage (Lw –

liquid water; Lc – carbonic liquid; V – vapour; Sh – solid halite; nS – multiple solids).

Microthermometric data were collected using a Linkam THMSG 600 heating and

freezing stage which was calibrated at -56.6ºC, 0ºC, and 10ºC using synthetic fluid

inclusion standards and distilled water, and at high temperatures using a range of pure

solids. All measurements were made during heating runs to avoid problems of

metastability. At low temperatures (<30C) heating rates of 0.5C/min were used,

with a precision of ±0.2ºC, and rates of 5C/min, with a precision of ±1ºC for

measurements of solid dissolution and liquid-vapour homogenisation temperature

(Th). Key samples were photographed and inclusion locations accurately mapped for

location for subsequent LA-ICPMS analysis of inclusion chemistry.

Fluid inclusion salinities were calculated as weight % NaCl equivalent (wt. %

NaCl eq.) directly from halite dissolution (Sterner et al., 1988), from ice melting

temperatures (Bodnar, 1993), and from clathrate melting in the Q2 assemblage

(Lw+Lc+V+Clathrate; Diamond, 1990). Where possible NaCl:CaCl2 ratios where

estimated using the ice melting temperature and the halite dissolution temperature (for

halite saturated inclusions; Williams-Jones and Samson, 1990), and the hydrohalite

melting temperature (for halite undersaturated inclusions; Oakes et al. 1990) . The

composition of Lw+Lc+V inclusions was calculated from ThCO2,, salinity calculated

from TmClath and estimated volume proportions of the gas phase using the BULK

program (Bakker, 2003) using the Archer (1992) ion interaction model and the gas-

fluid-salt mixing model of Krumgalz et al. (1996). Isochores for all inclusions except

Lw+Sh+V inclusions were calculated using the ISOC program (Bakker, 2003) and the

equations of state for the NaCl-CO2-H2O system of Bowers and Helgeson (1983), for

the system NaCl-CaCl2-H2O of Zhang & Frantz (1987), and the pure CO2 system of

Span & Wagner (1996). The position of the halite solidus and estimates of pressure at

homogenisation from Lw+Sh+V inclusions were calculated using the equations of

Bodnar (1994) and Becker et al., (2008). Estimates of the pressure at total

homogenisation of Lw+Sh+V inclusions homogenising by halite dissolution are very

approximate because many measurements are not covered by the experimental range

of Becker et al., (2008). The bulk salinities calculated for these inclusions using the

equation of Sterner et al. (1988) are also likely to be slightly under estimated (Bodnar,

1994; Becker et al., 2008), but the error on a calculated salinity is likely to be ≤1wt.%

NaCl eq.

3.2 Crush-leach analysis

To produce enough leachate for major, minor and trace element analyses, quartz vein samples

were cleaned and hand-picked to produce a total of 5g of material. The samples were then

washed in 18.2 m water and heated overnight on a hot plate, then dried in an oven. Two

grams were crushed and leached in a clean environment using the technique described in

Gleeson and Turner (2007). All the leachates were analysed by a DX600 ion chromatograph

for Cl-, Br

-, F

-, sulphate and phosphate, and for Na by atomic adsorption spectroscopy.

Replicate analyses were within 2% for Cl- and SO4

2- and 5% for F

-, Br

- and Na

+. This leachate

was also analysed for chlorine stable isotopes (Gleeson & Smith 2009). The second aliquot of

sample was leached with a La-dosed solution and this was analysed by ICP-MS and atomic

emission spectroscopy for Na, Ca, Fe, Mn, K, Mg, Pb, Zn, Sr, Ba, Al, Cu, B, Li, Co, As, Cd,

Si, S, Sb, Be, Cr, Mo, Ni, Se Ag, Tl, Sn, Ti, U and V. Of these elements, Na, Ca, Fe, K, Pb,

Zn, Sr, Ba, Al, Cu, B, Li, Co, As, Cd and Si were routinely detected in the samples.

Analytical precision on these elements is typically within ±5%.

3.3 Laser Ablation ICP-MS

Fluid inclusions were analysed following the method of Allan et al. (2005)

using a GeoLas Q Plus Excimer laser (ArF, 193nm, Microlas, Göttingen, Germany).

Ablated material was transported from a cylindrical chamber with a height of 5 mm

and internal diameter of 57 mm (approximately 13 cm3) in 0.68 L/min He via

Teflon® tubing to a cyclone gas mixer, where the analyte was premixed with 0.95

L/min Ar before introduction into the plasma. The analyte was analysed with an

Agilent 7500c quadrupole ICP-MS, equipped with an octopole reaction cell that was

pressurized with 2.5 mL/min H2, which virtually eliminated 40

Ar+ and

40Ar

16O

+

interferences on 40

Ca+ and

56Fe

+, respectively, and greatly reduced the high Ar-based

backgrounds on 39

K+. Fluid inclusion analyses were calibrated using combinations of

NIST SRM 610 and 612, an in-house EMPA glass standard, and HNO3 spiked

aqueous standards ablated directly through the walls of glass capillaries (Ghazi and

Shuttleworth, 2000; Günther et al., 1997; Boué-Bigne et al., 1999). Silicate glass

standards were ablated for 200 pulses over a single 50 m spot, using a repetition rate

of 5 Hz and laser fluence of 10 J/cm2. Laser focus on the ablation surface was

maintained by raising the ablation cell 1m per 10 shots, in accordance with an

approximate ablation rate of 0.1 m/pulse. Sodium was used as the internal standard

in all cases. Sets of fluid inclusion analyses were bracketed by standards, and linear

drift corrections were applied. Dwell times were 5 - 15 ms.

The absolute concentration of cations in analysed inclusions, and in bulk leachates

was calculated by charge balance of the total cations against a Cl molality determined

from microthermometric data wherever possible (Allen et al., 2005). An octopole

reaction cell was not used for the analyses including Br and Cl to maximise the

sensitivity on those elements, but this allowed polyatomic interferences on some

elements which were consequently omitted from the element list (40

Ca+,

56Fe

+,

39Ca

+ -

Allan et al., 2005). In the case of analyses of inclusions for Cl and Br therefore, where

a limited element list was used, the element ratios from the analyses were normalised

to the total Cl concentration in ppm. Limits of determination varied according to

inclusion, and were defined as 6σ in the background counts. Signals below this limit

were rejected *

4. Results

4.1 Fluid inclusion petrography

The petrography of fluid inclusions from the samples used here is described in

Gleeson and Smith (2009) and is summarised briefly in Table 2 and Figure 3. In late

stage quartz veins from the Fe oxide-apatite deposits, along with Lw+Sh+V (Fig. 3A)

inclusions trapped on annealed trails, inclusions of consistent microthermometric

properties occur in settings interpreted as primary, in growth zone parallel trails (Fig.

3B), or isolated in grain cores. Metastable Lw+Sh inclusions occur which nucleated a

vapour bubble on freezing. The sample from the Henry Fe-oxide-apatite body is

notable in that halite-bearing inclusions showed a double meniscus and a small

amount of CO2 within the inclusion (Fig. 3C). In Pahtohavare and other relatively

undeformed IOCG deposits the inclusions (typically Lw+nS+V; Fig, 3D) are

likewise trapped in primary settings, notably in vein wall parallel trails or as randomly

distributed groups, overgrown by inclusion free rims (Fig. 3E, F). Secondary trails are

dominated by CO2-rich inclusions (Lindblom et al., 1996). The majority of samples

from undeformed Fe oxide-apatite and IOCG deposits were analysed by crush-leach

techniques, with selected samples from Kiruna, Nuktus and Pahtohavare also analysed

by LA-ICPMS.

At Nautanen and other NDZ-related deposits all the inclusions analysed were

trapped in annealed fractures. Halite-bearing inclusions can be divided into those that

occupy discrete trails of a single inclusion phase assemblage, and those that form part

of an assemblage with an Lw+Lc+V inclusion population. The highest salinity

inclusions (Fig. 3G) are similar to those noted as primary in the Aitik deposit by

Wanhainen et al., (2003). The inclusion assemblage from deposits associated with the

NDZ includes coexisting Lc+V (Fig. 3H) Lw+Lc+V and Lw+Sh+V (Fig. 3I)

inclusions. The Lw+Lc+V and Lc+V inclusions are in some instances preserved along

the same secondary fluid inclusion trails (Fig. 3J) suggesting phase separation. These

complex inclusion assemblages were targeted for LA-ICPMS analysis in order to

investigate the chemistry of inclusions of contrasting room temperature phase

assemblage within the same overall inclusion assemblage.

4.2 Microthermometry

The results of fluid inclusion microthermometry are summarised in Tables 2

and 3, and shown in Figure 4. In Lw+Sh+V inclusions in quartz veins from Fe oxide-

apatite deposits first melting temperatures ranged from -68°C to -50°C, indicative of

NaCl-bearing solutions containing a range of other monovalent and divalent cations

(most likely including CaCl2 and FeCl2). The salinity of these inclusions, with the

exception of a single sample from the Mertainen deposit (52 wt. % NaCl eq), varies

from 30.4 to 41.2 weight % NaCl equivalent. Estimates of bulk salinity in the system

NaCl-CaCl2-H2O range from 34 to 47 wt. % NaCl+CaCl2 eq., with NaCl-CaCl2 mass

ratios from ~1 to 6 (Table 3; Fig. 4A). In the Lw+Lc+Sh+V inclusions from the

Henry deposit clathrate melting was never observed, and decrepitation prior to total

homogenisation (Th) was common. Estimation of inclusion composition from

microthermometric data and estimates of phase volume proportions suggests salinities

from 33 to 38 wt. % NaCl eq., with XCO2 in the bulk inclusion ranging from 0.01 to

0.03. This sample also included a secondary population of Lw+Lc+V inclusions

(Table 3) with compositions of ~21.5 wt. % NaCl eq. and XCO2 ranging from 0.03 to

0.06.

Primary, pseudosecondary and secondary inclusions from relatively

undeformed IOCG deposits are Lw+nS+V halite-bearing inclusions, with the main

solid being halite. Microthermometric and laser Raman spectroscopic investigations

by Lindblom et al. (1996) also identified sylvite, calcite, hematite and graphite in

inclusions from Pahtohavare. Lw+Sh+V inclusions dominate in the sample from

Kiskamavaara. Secondary trails of Lc+V inclusions are common. In most cases,

salinities ranged from ~40 to ~58 wt. % NaCl eq. The fluids are NaCl dominated,

with NaCl:CaCl2 ratios ranging from ~6 to 21. Lw+Sh+V inclusions at Kallosalmi

and Pahtohavare, Kiskamavaara, and Gruvberget range in salinity from ~30 to 38 wt.

% NaCl eq (Table 3; Fig. 4B). The Lc+V inclusions have TmCO2 temperatures

ranging from -56.6 to 60°C, indicating CO2-dominated fluids. Lindblom et al. (1996)

identified N2 in addition to CO2 in this inclusion type. Carbonic phase

homogenisation was always to the liquid and ranged from -16 to 22°C. A secondary

population of Lw+V inclusions was observed in samples from the Gruvberget deposit.

These show Tmice from -6.8 to -45 and Tmhh from -30 to -48°C, consistent with Ca-

rich brines (Oakes et al., 1990; Table 3; Fig. 4B). This population has been noted

from other deposits in the area (Broman and Martinsson, 2000; Wanhainen et al.,

2003).

All samples analysed from deposits and prospects within or near the Nautanen

Deformation Zone (NDZ) have complex fluid inclusion assemblages and parageneses

(Wanhainen et al., 2005). Halite-bearing inclusions in discrete trails have similarities

to those observed in the Fe oxide-apatite deposits and the IOCG deposits (salinity

from 31-52 wt. % NaCl eq. and ThL-V from 138-196ºC; Table 3 Fig. 4C). Separate

populations of Lw+Sh+V inclusions with salinity from 30 to 26 wt. % NaCl eq. and

ThL-V from ~120 to 180°C also occur. Secondary Lw+V inclusions have ThL-V

range from ~110 to 200°C, and fall into two broad compositional groups: a Ca

dominated brine, with salinities from 22 to 33 wt. % NaCl eq. and NaCl:CaCl2 ratios

ranging from 0.2 to 0.5 and a more Na-rich fluid with salinities from 22 to 26 wt. %

NaCl eq. (~20 to 24 wt % NaCl+CaCl2 eq.) and NaCl:CaCl2 ratios ranging from 0.5 to

1.3 (Table 3).

In samples from both Nautanen (NAU77006 210.47m) and Aitik (A3) more

complex assemblages occur on individual trails (Fig. 3j) with trails noted with

assemblages including [Lw+V plus Lw+Lc+V], [Lc+V plus Lw+V plus Lw+Sh+V],

[Lw+V plus Lw+Lc+V plus Lw+Sh+V] and [Lw+Sh+V plus Lc+V]. These are

shown in square brackets to highlight assemblages on individual planes. Care must be

taken with both the Lw+V and Lc+V inclusions in these examples as these may have

small amounts of either the carbonic phase of aqueous phase respectively as thin films

that were not observed microscopically. Aqueous liquid plus halite plus vapour

inclusions from these assemblages range in salinity from 28 to 35 wt. % NaCl eq. and

homogenise between approximately 100 to 200°C (Fig. 4C). Aqueous liquid plus

vapour inclusions from Nautanen range in salinity from 12 to 24 wt. % NaCl eq., with

NaCl:CaCl2 ratios typically ~1. Aqueous liquid plus carbonic liquid plus vapour

inclusions at Nautanen and Aitik range in salinity from 4 to 21 wt. % NaCl eq. in the

aqueous phase, with XCO2 ranging from 0.02 to 0.29. Homogenisation to the liquid

phase typically took place in the range 200-300°C. Carbonic liquid plus vapour

inclusions mostly showed TmCO2 from -56.6 to -59.0°C, with the majority of data

between -56.6 and -57.0°C indicating a CO2 dominated carbonic phase. These

inclusions showed a wide range of densities, and homogenised to both the liquid and

the vapour phase.

4.3 Crush leach and Laser Ablation ICP-MS analyses

The results of crush leach analyses are shown in Table 4, and representative LA-

ICPMS analyses are shown in Table 5. The full data set for LA-ICPMS analyses is

shown in the electronic Appendix. In all cases, the cationic composition of the brines

is dominated by Na, Ca, K and Fe. In rare instances, the Fe concentration exceeded

the K concentration. Concentrations of Mn, Sr, Ba, Zn, and Pb, are also significant,

exceeding 1000 ppm in reconstructed fluid compositions in a number of cases.

Copper concentrations are comparable in both data sets, ranging from tens to

hundreds of ppm, and in rare case up to a few 1000, notably in individual fluid

inclusion LA-ICPMS analyses compared to lower values in samples analysed by

crush-leach methods. Boron and Li concentrations from the crush leach analyses are

typically low, with Li below detection limits in some instances. Crush leach analyses

also show significant sulphate concentrations in most fluids, ranging from ~10 to

5000ppm.

The results of crush leach and LA-ICPMS analyses are compared in Table 6.

Analytical precision on leachate analyses is typically ~5%, whilst Allan et al. (2005)

found accuracy typically around 15%, and precision was around 15%RSD for K, Rb

and Cs, and 30% for other elements using LA-ICPMS. We have chosen to show a

30% error for all elements analysed by LA-ICPMS. Given that the crush-leach

analyses represent a composition homogenised over many inclusions within a large

sample of quartz whilst the LA-ICPMS analyses are analyses of a limited number of

individual inclusions the two data seta are reasonably consistent. For Fe oxide–apatite

and IOCG-type fluids there is good agreement between crush-leach and LA-ICPMS

analyses for individual samples for Na, Fe, K, Ca, Mn, Cu and B. There is greater

spread in the LA-ICPMS data, as would be expected from the relatively low analytical

precision, and from the analysis of individual inclusions, which trapped fluids during

different stages of wall-rock interaction, precipitation and potentially mixing.

However, significant differences do occur for K (in some samples), Ca (in some

samples), Ba, B, and Br. Potassium values are only inconsistent for the sample from

Kirunavaara where they are higher in the LA-ICPMS analyses than in the crush leach

analyses. This may therefore represent sampling bias in the LA-ICPMS analyses.

Although the microthermometric and LA-ICPMS data confirm that high Ca

concentrations are characteristic of some fluids, the crush leach data gives some

anomalously high Ca values. These may be related to contamination of the leachate

by calcite on fracture surfaces. There is poor agreement between crush-leach analyses

and LA-ICPMS data for Br. This is likely to be because Br only exceeded detection

limits for LA-ICPMS in a limited number of the most saline and Br-rich inclusions.

Bromine analysis of fluid inclusions by the methods used here has also been noted to

give anomalously high Br concentrations from synthetic fluid inclusions (Allan et al.,

2005), which Seo et al. (2011) attributed to remobilisation of Br from the ablation

chamber and sample surface. As a result, Br/Cl ratios for inclusions analysed by LA-

ICPMS are not included in the discussion and figures below.

5. Discussion

5.1 Trapping and ore formation conditions

For the vast majority of inclusions from the Fe oxide-apatite and IOCG

deposits in this study there are a scarcity of relevant experimental data to constrain

pressures at homogenisation and the positions of isochors. Very approximate

estimates of P at Th can be made from the data of Becker et al. (2008) by comparison

of Tsolhalite and ThL-V with calculated isobars (Fig. 5A-C). Generally minimum

trapping conditions for ‘Fe oxide-apatite type’ fluids are from 200-350°C and 200-

>300MPa, with those in chalcopyrite bearing veins from the Henry deposit potentially

being even higher because of the presence of CO2 (Schmidt and Bodnar, 2000), whilst

those for ‘IOCG type’ fluids are from 300-450°C and 250 to >300MPa.

Early stages of fluid circulation at Aitik and Nautanen presumably took place

under similar conditions to those seen in less deformed deposits (Wanhainen et al.,

2005). The presence of secondary inclusion assemblages with complex mixtures of

room temperature phase assemblage may provide better evidence for trapping

conditions if they represent an unmixing assemblage (Fig. 5 D, E). Inclusions that

homogenise by halite dissolution cannot represent part of an aqueous-carbonic fluid

immiscibility assemblage, but mixed assemblages of Lw+Lc+V and Lc+V inclusions

can, as can halite bearing inclusions which homogenise by vapour disappearance. For

the sample studied at Aitik all Lw+Sh+V inclusions homogenise by halite dissolution,

and so cannot have been formed by immiscibility. They hence indicate the presence of

a fluid with salinities in the range 28-30 wt. % NaCl eq., comparable to fluids in veins

cross-cutting the Fe oxide-apatite deposits. Aqueous-carbonic inclusions in trails with

mixed Lw+Lc+V and Lc+V inclusions have estimated homogenisation pressures of

250-350MPa at temperatures of 200-290ºC, which provide minimum estimates of

trapping conditions. Isochors for Lc+V inclusions which homogenise to a carbonic

liquid do not intersect with those of the Lw+Lc+V inclusions and so either do not

represent part of an unmixing assemblage, or more likely given that these inclusion

types occur on the same trails, contain a film of water which was not visible using

transmitted light microscopy and hence may have homogenised at higher T and P than

observed. The presence of Lc+V inclusions that homogenise to a carbonic vapour

suggests pressures may have dropped even lower during periods of fracturing and

vein dilation.

At Nautanen Lw+Sh+V inclusions homogenising by halite dissolution are also

common, and so indicate similar saline fluids to those seen at Aitik. However, saline

Lw+V inclusions, Lc+V, and Lw+Lc+V inclusions do co-exist, alongside some

Lw+Sh+V inclusions which homogenise by vapour disappearance. Isochors for co-

existing Lw+Lc+V, Lc+V, and Lw+V inclusions intersect (Fig. 5E), but do not have

the same homogenisation temperature and pressures as would be required for

definitive evidence of aqueous-carbonic fluid immiscibility (Ramboz et al., 1982).

However, thin films of aqueous or carbonic fluids may be microthermometrically

undetectable in the Lc+V and Lw+V inclusions respectively meaning that the trails

with secondary populations are still consistent with immiscibility. The alternative, of

mixing of aqueous and carbonic fluids cannot be ruled out, but would have been

unlikely because of the difference in fluid density. In the case of immiscibility the

homogenisation temperatures and pressures of the Lw+Lc+V inclusions indicate

ranges ~240-370ºC and ~130-160MPa, and ~250-280 ºC and 25-55MPa. The wide

range in homogenisation pressure is consistent with changes in fluid pressure during

shear zone movement. The samples from the Ferrum Au prospect, peripheral to the

main NDZ (Fig.5F), have a saline inclusion population with isochors similar to those

from the saline populations from Aitik and Nautanen, but have no carbonic or

aqueous-carbonic inclusions. The conditions of trapping of secondary calcic brine

inclusions in all deposits cannot be constrained beyond the plotting of representative

isochors (Fig. 5F).

5.2 Source of salinity in the fluids.

Gleeson and Smith (2009) examined the potential sources of salinity in the

sample set studied here using Br and Cl concentrations and chlorine stable isotope

ratios. They concluded that whilst the Br/Cl ratios could be derived from either

magmatic sources or halite dissolution, 37

Cl values of Fe oxide-apatite and IOCG

mineralisation-related quartz veins were lower than most crustal values and, hence,

suggested magmatic input. However, some 37

Cl values were very low and it was

suggested that these may be the result of fractionation during extensive fluid-rock

interaction between the fluids and Cl-rich phases (biotite and scapolite). The Br/Cl

ratios and 37

Cl values of vein fluids in NDZ-related deposits indicated a crustal

origin for salinity and could indicate that the fluid salinity was sourced from either

evaporites or from input from crustal melts, such as the granitic pegmatites of the

Lina Suite that cut the Aitik deposit (Gleeson & Smith, 2009).

In this study, although a number of samples have Cl/Br ratios consistent with a

magmatic source for the halogens, the Cl-enrichment apparent in the extended dataset

(Fig. 6A),could be a strong indicator of interaction of fluids with (meta-) evaporites

and consequent halite dissolution (Fig. 6B), followed by extensive water-rock

interaction (Gleeson and Smith, 2009). No single group of inclusions or sample type

shows a range of ratios consistent with a single fluid source, nor do high Cl/Br ratios

correlate with the highest salinity fluids (Fig. 6C), which indicates that halite

dissolution was not the only mechanism which generated highly saline brines. Typical

magmatic-hydrothermal fluids are expected to have low salinities (Candela, 1989) and

salinities of ~6wt % NaCl eq. were used by Barton and Johnson (2000) for mass

balance models of IOCG deposit formation. In this situation, however, highly saline

magmatic brines could be produced by aqueous-carbonic fluid exsolution from

magmas at relatively high pressure (compared with the porphyry environment) with

subsequent separation and loss of water to a carbonic phase resulting in a high-salinity

magmatic brine (Pollard, 2006). Brines associated with the NDZ show less evidence

from Cl isotopes for fluid-rock interaction (Gleeson and Smith, 2009) and are

significantly removed in time and tectonic setting from those involved in the

formation of Fe oxide-apatite and IOCG mineralisation (Smith et al., 2009).

The complex range of sources for fluid components inferred above are

consistent with the picture from IOCG type mineralisation globally, with deposits

showing a complex mix of brine sources including magmatic-hydrothermal,

evaporitic and surface fluids (e.g. Kendrick et al., 2007, 2008b) with some examples

of deposits dominated by a single end-member (c.f. Williams et al., 2001). There

remain issues with mixing models as the fluids involved frequently show high density

contrasts, and there is abundant evidence for fluid overpressure in the form of

hydraulic breccias in many districts, both of which would inhibit fluid mixing.

5.3 Controls on major element chemistry

The major element chemistry (Na, Ca, K, Fe and Mn) of crustal brines is

controlled either by mineral-fluid equilibria, or, in cases where the buffer capacity of

the host rock is exceeded, by the initial composition of the brine and the water-rock

ratio (Yardley, 2005). It is rare in any of the deposits studied to see two feldspars in

equilibrium, as albite replaces intermediate plagioclase in volcanic host rocks, and

potassic alteration producing K-feldspar and biotite is common. Thus, the second of

the two cases above is more applicable to the alkali and alkaline earth metal

concentrations in the hydrothermal systems. Most fluids are depleted in Na relative to

the trend of halite dissolution by seawater. The Na-depletion is likely to relate to Na-

Ca exchange reactions (albitisation and scapolitisation). The microthermometric data

show that fluids in veins associated with Kiruna-type and IOCG mineralisation are

strongly enriched in Na relative to Ca (Fig.7) and the LA-ICPMS and crush-leach data

show that, except for in the late stage vein from Kiirunavaara, they are enriched in Na

relative to K. The higher K content of the late Kiirunavaara brines suggests that the

fluid trapped here is closer to a composition buffered by two feldspars, and potentially

represents a less evolved fluid. In all these fluids K shows a strong positive

correlation with Ba and Ba-rich K-feldspar has been reported from the IOCG deposit

at Tjarrojakka (Edfelt et al., 2005).

At Gruvberget, and in both Aitik (Wanhainen et al., 2003) and Nautanen,

strongly Ca-enriched fluids are found in secondary inclusions. The correlation of high

Ca with high Na/K ratios (Fig. 7) is consistent with these fluids reacting with feldspar

bearing assemblages at lower T than in the Fe oxide-apatite and IOCG related brines.

High Ca contents can also be facilitated by low CO2 fugacities, possibly following

phase separation, resulting in a lack of buffering of Ca contents by calcite

precipitation (Yardley, 2005). At Aitik, Wanhainen et al. (2003) attributed Ca-rich

fluids to interaction of fluids with evaporites and anhydrite/gypsum dissolution.

However, no concomitant increase in sulphate is seen, and there is little or no

evidence of evaporitic sulphur in the region (Frietsch et al., 1995). The only other

major source of Ca-rich fluids would be the dissolution of limestone. Intense

magnetite and calc-silicate skarns do occur in the area (distinct from the magnetite-

apatite deposits) and hence limestone destruction may have acted as an additional

source of Ca.

The fluids vary significantly in Fe content, in some cases to the extent that the

brines are in fact Fe-dominant chloride solutions. This in part reflects the strong

control of chlorinity on Fe solubility in most relatively reducing environments (Chou

and Eugster, 1977; Kwak et al., 1986; Yardley, 2005). Iron was effectively mobilised

from a volumetrically extensive zone during the regional albitisation and

scapolitisation events that affected the Fennoscandian shield in northern Sweden and

western Finland (Freitsch, 1997; Niiranen, 2005). Iron solubility is also controlled to a

lesser degree by temperature and oxygen fugacity (Chou and Eugster, 1977;Yardley,

2005). The latter can be examined using the Fe/Mn ratio (Bottrell and Yardley, 1991),

as Fe and Mn should exhibit contrasting redox behaviour. Unsurprisingly the Fe/Mn

ratio correlates positively with the Fe content (Fig.8A). The data from the Nautanen

prospect and Aitik deposits show lower Fe contents at a specific Fe/Mn ratio

compared the Fe oxide-apatite deposits and IOCG-type deposits reflecting lower P-T

conditions of trapping, and potentially different, Mn-depleted, host rocks. Copper

concentrations show no correlation with the Fe-Mn ratio (Fig. 8B), suggesting a less

significant redox control on copper solubility..

5.4 Metal transport and deposition

For a given source rock or magma the primary constraints on the metal

bearing capacity of a hydrothermal solution are the availability of ligands, the

temperature, the pH and the redox conditions (Barnes, 1979; Seward and Barnes,

1997; Wood and Samson, 1998; Yardley, 2005). In a significant proportion of natural

solutions chloride is the predominant available anion for aqueous complex formation,

although HS- maybe important for some metals (Seward and Barnes, 1997). Figure 9

shows plots of metal content against overall salinity. Within the relatively broad range

of analytical values it is clear that salinity, and by inference chloride concentration,

has a key effect on metal concentrations. Both pH and fO2 are likely to have been

strongly buffered by the alteration (feldspars and phyllosilicates) and oxide and

sulphide mineral assemblages (magnetite-pyrite-hematite) in these deposits, and both

are difficult to directly assess on the basis of fluid inclusion analyses alone. The

effects of temperature are examined in Figure 10A-C, using fluid inclusion

homogenisation temperatures (either halite dissolution or L-V homogenisation) as a

proxy for trapping temperature. Correlations between T and metal concentration are

poor for most metals with exception of Fe and Ag, which, despite the order of

magnitude variations at any given T, show distinct high concentration clusters at high

T (Fig. 10B). There may be some masking of the true trend here as the Th values used

are not corrected from pressure at trapping. Also the spread in data may be affected by

the water-rock interaction history and the extent of equilibration with Fe-minerals.

The effects of chlorinity can be normalised for by using the molal Me/Cl ratio

(Yardley, 2005). Examples of these plots are shown in Figure 10F-H, which support

interpretations of the influence of T on the solubility of Fe. For some transition metals

(Cu and Pb) such a relationship is not apparent.

Cu contents in the hypersaline brines of the Pahtohavare deposit are typically

in the range 100-500ppm, although some inclusions here and in the late stage

Kiirunavaara veins have in excess of 1000ppm Cu. These ranges are comparable to

saline magmatic fluids from the Cloncurry district, Australia (Baker et al., 2008), and

are consistent with conclusions of Cu transport in saline brines in porphyry systems

(Lerchbaumer and Audetat, 2012) The highest Cu contents are, however, in lower

salinity and temperature fluids from the NDZ. Previous work has identified solid

sulphide inclusions on secondary trails in quartz from Aitik (Wanhainen et al., 2003),

but these were not observed in the samples used in this study, and so we conclude that

the data reflect real inclusion metal concentrations. A key control on elevated Cu

concentrations may be high Cu contents in the source rocks and along the flow paths

of the later hydrothermal fluids at Aitik and Nautanen, and, hence, a closer approach

to saturation with Cu phases when compared to the earlier Fe oxide-apatite fluids

(c.1890-1870Ma) and IOCG fluids (c. 1870-1860Ma). This interpretation is supported

by Nd isotope data which indicate distinct sources for the two main mineralisation

stages (Storey and Smith, in prep.). However, there is still a contrast between halite-

bearing fluid inclusions and aqueous-carbonic brines at Nautanen and Aitik, which

suggest other factors may also be important.

Diffusional loss or gain of Cu+ in fluid inclusions has been demonstrated

experimentally (Li et al., 2009; Lerchbaumer and Audetat, 2012) via interdiffusion

with Na+ and H

+, and to a lesser extent down concentration and electrochemical

potential gradients. These studies involved Cu diffusion into very low salinity vapour

inclusions, rather than the saline (10-20 wt. 5 NaCl eq.) aqueous-carbonic fluid

observed here and so the conditions of the experiments did not reproduce those seen

here. Analyses of some aqueous and aqueous carbonic fluid inclusions on single

secondary trails show very consistent Cu contents (Appendix – NAU7706s)

interpreted as trapping from a relative homogenous fluid in this case, and suggesting a

lack of modification by post-entrapment diffusion. However, post-entrapment

modification of inclusion Cu content cannot be entirely ruled out.

If high Cu contents in aqueous-carbonic fluids are not caused by post-

entrapment modification, then the lack of correlation of high Cu with the most saline

brines suggests complexation of Cu by ligands other than Cl. Sulphur concentrations

(as sulphate) are only available from crush-leach analyses in this study, but Figure 11

shows positive correlations between SO42-

and Cu concentration. Yardley et al. (1993)

argued that crush-leach techniques are S-species specific, with H2S escaping the gas

phase during crushing. The oxygen fugacity and pH in ore mineral assemblages in

these rocks are likely to have either been buffered by the assemblage pyrite plus

magnetite, or in the NDZ-related deposits by assemblages including pyrrhotite. The

positions of pyrite-magnetite boundary and the pyrite-pyrrhotite-magnetite triple point

would in part also be controlled by the total sulphur content of the fluid (Bowman,

1998). For the lowest sulphate contents analysed here H2S and HS- would also be

significant components of the fluid, whilst in the highest sulphate content fluids SO4-

would predominate, but there would still be significant reduced S species. Hence, the

order of magnitude variations in sulphate content of the leachate fluids may be taken

as also indicate major variations in the concentration of the reduced sulphur species

(Fig. 11). This suggests a role for complexation of metals by sulphur species,

probably HS-, in these fluids. High concentrations of sulphide species in low salinity

fluids are consistent with the lower solubility of volatile species in aqueous solution

with increasing salinity. Halite-bearing inclusions from both Aitik and Nautanen show

lower Cu, Ag and Au concentrations than co-existing Lw+V and Lw+Lc+V

inclusions. H2S solubility in aqueous fluids decreases with increasing salt content with

little temperature dependence except close to the critical point of water (Suleimanov

and Krupp, 1994; Duan et al., 1996) in a similar way to CO2. Data on CO2-H2S

miscibility are lacking, but in most natural fluids H2S concentrations are unlikely to

be high enough to result in separation of two volatile-rich fluids and H2S would

remain completely miscible with a CO2-rich aqueous carbonic phase. It is therefore

reasonable to suppose that bisulphide complexation will lead to elevated

concentrations of metals acting as ‘soft’ Lewis acids (Cu, Au, Ag; Robb, 2005) in

relatively low salinity, aqueous-carbonic solutions. The data presented here indicate

that post-primary ore stage aqueous and aqueous-carbonic fluids in the NDZ hosted

deposits, derived from either the local meta-volcanosedimentary rocks or from Lina

stage crustal melts (Gleeson and Smith, 2009), transported significant Cu, Ag and

possibly Au, resulting in grade increases as a result of addition of new metal, or by

remobilisation of the primary ore. In mixed-volatile fluids, water activity coefficients

rise above 1 at low pressures (~1.5kbar), but then fall with increasing temperature and

pressure (Shmulovich and Graham, 1996). Aqueous-carbonic fluids may therefore be

effective at forming outer sphere hydration shells (c.f. Williams-Jones and Heinrich,

2005) despite a lowered dielectric constant in the mixed solvent (Walther and

Helgeson, 1980; Walther and Orville, 1983; Fein and Walther, 1987, 1989), at

relatively shallow crustal depths, although there may be a preference for the

occurrence of neutral complexes in solution.

The fact that mixed Lw+Sh+V, Lw+Lc+V and Lc+V inclusions exist on

individual trails may be indicative of aqueous-carbonic fluid immiscibility. It has not

been possible in this study to present full analyses of the CO2-rich inclusions in these

assemblages, as salinity could not be determined microthermometrically. Studies of

vapour phase transport all emphasise the role of bisulphide complexation in the low

density phase (e.g. Heinrich et al., 1999; Ulrich et al., 1999; 2001; Williams-Jones

and Heinrich, 2005). It has now been demonstrated that S partitions strongly into the

vapour phase on boiling in porphyry-type environments (Seo et al., 2009), and similar

behaviour would be expected in aqueous-carbonic fluid immiscibility. However, at

high XCO2 outer sphere hydration shells implicated in vapour phase transport

(Williams-Jones and Heinrich, 2005) would breakdown, and so analogous behaviour

of metals during aqueous-carbonic fluid immiscibility may not occur, and the

preferentially partitioning of H2S into the carbonic phase may actually be a trigger for

metal deposition (Robb, 2005). The primary nature of high Cu contents in vapour

inclusions has also now been called into question (Lerchbaumer and Audetat, 2012),

suggesting immiscibility may be an effective trigger for Cu and possibly precious

metal deposition. A full interpretation of these effects will require further analyses of

CO2-rich fluid inclusions.

6. Conclusions

The Fe oxide-apatite and IOCG deposits of the Kiruna and Malmberget

districts, Sweden, formed from contrasting high salinity fluids at different times

during the evolution of the districts. Deposits associated with major deformation

zones show similar early fluid inclusions, but all have strongly overprinting fluid

inclusion assemblages, with lower (but still highly saline) salinities, the presence of

aqueous-carbonic fluids, and potentially immiscibility at some stages. These latter

fluids are potentially related to a separate stage of hydrothermal circulation at

~1780Ma. Microthermometric constraints indicate minimum P-T conditions for Fe

oxide apatite mineralisation of ~200-350°C and 200-300MPa and for IOCG

mineralisation of ~300-450°C and 250 to >300MPa. Co-existing aqueous-carbonic,

carbonic and saline fluid inclusions in deformed deposits associated with the NDZ

indicate formation during a fluctuating pressure regime, potentially with periods of

phase separation..

The Cl/Br ratios of inclusion fluids determined by crush-leach are consistent

with a range of fluid sources including both magmas and halite-bearing evaporates.

The major element concentrations of the fluids are variable, and change between

different stages of fluid circulation. Alkali metal concentrations appear to be

unbuffered by rock mineral assemblages, consistent with the extensive alkali

metasomatism in the area. Iron concentrations are strongly related to chlorinity, as are

other metals such as Pb, consistent with chloride complexation control on solubility,

with secondary controls from T and fO2. Copper concentrations (and potentially Ag

and Au) do not correlate with chlorinity in low salinity aqueous-carbonic fluids, and

although post-entrapment modification of Cu concentrations cannot be ruled out, are

inferred to be transported as bisulphide complexes in these lower salinity fluids. Low

to moderate salinity and aqueous-carbonic fluids may have high H2S concentrations,

relative to highly saline fluids, and hence similar to higher metal carrying capacity.

Acknowledgements.

This work was originally funded by European Union Regional Development Fund

Georange Program Grant 89121 to MS and SG. LA-ICPMS work was carried out at

the NERC JIF sponsored facility at the University of Leeds, U.K.

(NER/H/S/2000/853), with the assistance of L. Forbes and D. Banks. C. Storey

assisted with field work in Sweden. The manuscript was improved by constructive

comments from M. Barton and I. Samson.

Role of the funding source

The original field work and fluid inclusion work described in this manuscript were

funded by European Union Regional Development Fund Georange Program Grant

89121. Apart from specifically funding work related to metallogeny and mineral

exploration in Northern Sweden, this program played no role in the data collection or

interpretation beyond facilitating field work. The LA-ICPMS analyses were carried

out at the UK Natural Environment Research Council sponsored facility (NERC Joint

Infrastructure Fund) at the University of Leeds, U.K. (NER/H/S/2000/853). There is

no influence from the funders on the data collection at this facility.

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Tables

Table 1: Localities and descriptions of samples used in this study. Northings and

eastings are given in Swedish National Grid Co-ordinates (RTG80).

Table 2: Summary of fluid inclusion petrography and the results of

microthermometric measurements. All measurements in ºC.

Table 3: Summary of fluid inclusion compositions determined from

microthermometry.

Table 4: Representative results of analyses of fluid inclusion leachates from vein

quartz. Fluid compositions were reconstructed by charge balance of total

cations against Cl molality determined from microthermometric data (Allen et

al., 2005). All concentrations reported in ppm.

Table 5: Table 5: Representative examples of LA-ICPMS analyses of fluid inclusions.

Compositions are shown in ppm as either total cations charge balanced against

Cl molality from microthermometry (Allen et al., 2005) or normalised to Cl

concentration in ppm where the major cations had not been analysed.Table 6:

Comparison of reconstructed fluid composition from crush-leach analyses

with mean reconstructed fluid inclusion composition from LA-ICPMS

analyses. All concentrations in ppm.

Electronic Appendix: Results of microthermometry and LA-ICPMS analyses of fluid

inclusions, reconstructed from microthermometrically determined salinity

using the method of Allan et al., (2005).

Figures

Figure 1: Geological sketch map of northern Norrbotten county, showing the locality

of the deposits and prospects used in this study. Geology adapted from

Bergman et al. (2001).

Figure 2: Meso- to microscale textures in quartz veins from the studied deposits. (a)

Quartz-actinolite vein cutting magnetite-albite altered wall rocks, Nuktus. (b)

Plane polarised, transmitted light photomicrograph of quartz-carbonate vein

cutting magnetite ore, Luossavaara. The vein hosts titanite, now partly altered

to rutile (sample L4.1). The highlighted area is magnified in (c). (c) Plane

polarised, reflected light photograph of area highlighted in (a). There is no

visible alteration of magnetite in the vein wall rock. (d) Quartz-chalcopyrite-

ankerite vein cutting magnetite-albite altered metavolcanic rock, Pahtohavare.

(e) Plane polarised, reflected light photograph of quartz-magnetite-sulphide

vein, Pahtohavare (P11). (d) Plane polarised, combined reflected and

trasnmitted light photograph of quartz-sulphide vein sample A3, Aitik.

Sulphide minerals below the surface of the sample in fractures in quartz are

visible as opaque areas. Act – Actinolite; Alb – Albite; Ank – Ankerite; Cpy –

Chalcopyrite; Prt – Pyrrhotite; Py – Pyrite; Qtz – Quartz; Mgt – Magnetite; Rt

– Rutile; Ttn – titanite.

Figure 3: Petrography of fluid inclusions in studied quartz vein samples. (a) Fragment

of polished wafer from N2.2 showing fluid inclusions along face parallel trails

and growth zones in quartz. See Gleeson and Smith (2009) for further

evidence for primary fluid inclusion origin. (b) Lw+Sh+V inclusion in quartz,

Nuktus. (c) Lw+Sh+Lc+V inclusions in quartz, Henry. (d) Lw+nS+V

inclusions in quartz, Pahtohavare. (e) Lw+nS+V inclusions in quartz,

Gruvberget. (f) Lw+Sh+V inclusion in quartz, Nautanen. (g) Lc+V inclusions

in quartz, Nautanen. (h) Lw+Sh+V in clear secondary trail, Aitik. (i) Single

secondary fluid inclusion trail bearing Lc+V and Lw+Lc+V inclusions,

Nautanen.

Figure 4: Results of fluid inclusion microthermometry in terms of ThL-V and total

salinity as wt. % NaCl eq, and NaCl-CaCl2 ratio from samples from (a) Fe

oxide-apatite deposits.; (b) IOCG deposits; and (c) Deformed deposits

associated with the NDZ.

Figure 5: Estimates of P and T at homogenisation and trapping for different deposit

types. (a)-(c) Comparison of microthermometric data from this study with

isobars of P (in MPa) at halite dissolution from Becker et al. (2008). In nearly

all cases studied here the homogenisation conditions are outside the calibrated

range. (d) Isochors for different fluid inclusion populations from Aitik sample

A3. (e) Representative isochors for fluid inclusions from the Nautanen Cu-Au

prospect. A – approximate range of P at Th for fluid inclusion homogenising

by halite dissolution. B – Zone of P at Th for the Lw+Lc+V inclusions

occupying secondary trails with Lc+V inclusions. These may indicate trapping

conditions for an immiscibility assemblage, and the conditions of at least one

stage of ore genesis. Termination of isochores for Lw+Lc+V inclusions

indicates P at Th. (f) Approximate range of P at Th, and representative

isochores for fluid inclusions from the Ferrum deposit. See text for details of

isochore location and phase boundary construction.

Figure 6: Halogen geochemistry of fluid inclusions from the Norrbotten district. (a)

Comparison of Cl and Br concentrations in reconstructed inclusion fluids with

the seawater evolution trends from Fontes and Matray (1993). (b) Molal Na/Br

and Cl/Br ratios compared with the ranges of ratios from seawater and

‘magmatic’ fluids, and the halite dissolution trend. (c) Plot of molal Cl/Br ratio

against fluid inclusion salinity determined from microthermometry.

Figure 7: Ternary plots of fluid inclusion major element chemistry (as mass %) from

crush leach and LA-ICPMS analyses. The shaded areas in each plot show the

range of Na:Ca ratios determined from microthermometry.

Figure 8: Plots of reconstructed Cu and Fe concentrations against Fe/Mn ratio of fluid

inclusion leachates and LA-ICPMS analyses.

Figure 9: Plots of reconstructed transition and precious metal concentration against

salinity as determined from microthermometry.

Figure 10: (a)-(e) Plots of metal concentration against fluid inclusion homogenisation

temperature. (f)-(h) Representative plots of molal metal/chloride ratio against

1/T. The normalisation of metal to chloride removes the effects of salinity on

concentration, and allows the effects of T to be more fully assessed.

Figure 11: Variation in key metal concentrations with sulphate content of fluid

inclusion leachates. Sulphur was not analysed by LA-ICPMS in this study.

 

Sample No Site Name Northing Easting Depth Description

Magnetite-(Hematite)-apatite bodies.

KR2 Kiirunavaara 7534661 1684696 Surface Quartz-actinolite-hematite vein in hanging wall metavolcanic breccia.

L4.1 Luossavaara 7538046 1685661 Surface Aplitic quartz-carbonate vein cutting magnetite ore.

HEN04 Henry 7539907 1686986 Surface Quartz-chalcopyrite vein cutting magnetite ore.

N1 Nuktus 7538978 1686396 Surface Quartz-hematite vein cutting chloritic schist.

N2.2 Nuktus 7540615 1687048 Surface Quartz-hematite-ankerite vein cutting hematite ore.

N2.5 Nuktus 7540615 1687048 Surface Quartz-amphibole vein cutting partially altered rock.

MER2 Mertainen 7520872 1710539 Surface Quartz-albite-tourmaline vein cutting magnetite ore.

Greenstone- and Porphyry- hosted Cu mineralisation

KALL91002 Kallosalmi 7541825 1693135 59.53m Quartz vein cutting biotite-scapolite-graphite schist

PAH88217 Pahtohavare 7527612 1680390 21.20m Quartz vein cutting biotite-scapolite schist.

PAH85117 Pahtohavare 7527159 1680702 152.14m Quartz-carbonate vein in biotite-scapolite schist.

P11 Pahtohavare 7527555 1680370 Surface Quartz-chalcopyrite-bornite vein.

K2 Kiskamavaara 7534093 1725127 Surface Quartz vein in hematite cemented K-altered metavolcanic breccia.

G6 Gruvberget 7515227 1719947 Surface Quartz vein from Stokenstrom mine spoil.

G5.1 Gruvberget 7515149 1719979 Surface Quartz vein with malachite cutting K-altered metavolcanics.

GRUV02 Gruvberget 7515134 1719951 Surface Quartz vein at sheared margin of ore body.

GRUV06 Gruvberget 7515255 1719961 Surface Quartz vein cutting magnetite ore body.

Nautanen Deformation Zone(NDZ)-hosted Cu mineralisation

NAU 77006 Nautanen 7463947 1719762 210.47m Quartz-chalcopyrite vein cutting biotite-actinolite schist.

NAU 77006 Nautanen 7463947 1719762 281.7m Quartz-chalcopyrite vein cutting biotite-actinolite schist.

NAU02 Nautanen 7463815 1719453 Surface Folded quartz vein in psammitic garnet schist.

NAU83009 Nautanen 7463843 1719634 110.90m Quartz-chalcopyrite vein cutting biotite schist.

NAU05 Nautanen 7463626 1719521 Surface Quartz vein cutting bornite mineralised bt-qtz-ep schist.

NAU09 Nautanen 7461151 1719406 Surface Foliation parallel quartz vein in biotite-magnetite schist.

FERR69205 Ferrum 7463076 1722146 72.75m Quartz vein cutting K-feldspar-epidote-actinolite altered schist.

FERR69203 Ferrum 7463080 1722150 54.58m Quartz vein with sulphides.

FERR69202 Ferrum 7463110 1722160 6.43m Quartz vein with malachite and bornite

A3 Aitik 7545020 1724300 Surface Quartz-chalcopyrite vein - main ore zone

         

Table 1: Localities and descriptions of samples used in this study. Northings and eastings are given in Swedish National Grid Co-ordinates (RTG80).

 

N Inclusion Type

Tfm Tm Tm Tm Tm Th Th T sol

Range CO2 hh ice Clathrate CO2 L-V Halite

Magnetite-(Hematite)-apatite bodies.

KR2 28 Lw+Sh+V P/PS/S -48 to -55 6 -35 102 224

L4.1 28 Lw+Sh+V P/PS/S -52 to -62 10 -29 122 278

HEN04 16 Lw+Sh(+Lc)+V P/PS/S -44 to -68 -56.9 5 -27 24.9 118 249

10 Lw+Lc+V PS/S -28 to -51 -57.1 -26.6 -11.2 21.6 212

N1 28 Lw+Sh+V P/PS/S -52 to -67 12 -30 150 225

N2.2 24 Lw+Sh+V P/PS/S -58 to -69 12 -28.8 103 252

N2.5 21 Lw+Sh+V P/PS/S -57 to -66 10 -27.8 110 258

MER2 25 Lw+nS+V PS/S -60 to -70 14 -27.3 145 437

8 Lw+Sh+V S -32 to -62 12.8 -24.5 106 108

Greenstone- and Porphyry- hosted Cu mineralisation

KALL91002 15 Lw+nS+V P/PS ND 139 404

11 Lw+Sh+V PS/S -66 to -72 101 207

6 Lw+V PS/S -51 to -53 -22.3 120 ND

PAH88217 16 Lw+nS+V P/PS/S ND 119 452

PAH85117 19 Lw+nS+V P/PS/S -44 to -59 -15.1 161 412

Lc+V PS/S -59.7 -6.2

P11 23 Lw+nS+V P/PS/S -54 to -63 11 -25.8 137 375

K2 27 Lw+Sh+V P/PS/S -58 to -70 15 -25.9 118 229

G6 22 Lw+nS+V P/PS -45 to -65 12 -26.9 119 352

8 Lw+Sh+V PS/S 128 336

G5.1 16 Lw+nS+V P/PS 130 246

21 Lc+V PS/S -57.1 8.6

GRUV02 14 Lw+Sh+V PS/S 105 185

21 Lw+V PS/S -53 to -72 -34.5 -13.3 -8.7 137

15 Lc+V S -56.6

GRUV06 28 Lw+V PS/S -56 to -70 -43.9 -36.5 98.2

Nautanen Deformation Zone(NDZ)-hosted Cu mineralisation

NAU 77006 13 Lw+Lc+V PS/S -40 to -59 -56.8 0.2 28.1 263

40 Lw+Sh+V PS/S -52 to -65 6.1 -23.7 196 247

48 Lw+V PS/S -43 to -72 -27.9 -15.2 155

15 Lc+V PS/S -56.7 6.3

NAU 77006 29 Lw+Sh+V PS/S -52 to -66 1.6 -26.3 138 188

20 Lc+V PS/S -56.6 2.6

03NAU02 7 Lw+Sh+V PS/S 154 199

7 Lc+V PS/S -56.6 -8.4

NAU83009 30 Lw+Sh+V PS/S -63 to -73 145 158

3 Lw+Lc+V PS/S -56.6 4 29.3 269

7 Lc+V PS/S -56.7 28.5

NAU05 26 Lw+Sh+V PS/S -52 to -57 -18.3 -27 173 345

26 Lw+V PS/S -72 to -76 -41.4 -27.6 136

9 Lc+V PS/S -56.7 -6.8

NAU09 26 Lw+Sh+V PS/S -53 to -70 -10.9 -34.3 162 231

12 Lw+V PS/S -52 to -58 -29.9 -22.8 132

A3 34 Lw+Sh+V PS/S -79 to -64 12.6 -28.3 111 131

39 Lw+Lc+V S -65 to -45 -57.4 -1.3 17.6 243

11 Lw+V S -62 to -58 104

16 Lc+V S -57.8 2.7

FERR69205 3 Lw+Sh+V PS/S 141 180

18 Lw+V PS/S -52 to -69 -36.6 -18.7 152

FERR69203 13 Lw+Sh+V PS/S -59 to -63 1 -28.8 156 212

16 Lw+V PS/S -64 to -72 -35.3 -24.7 135

FERR69202 27 Lw+V S -66 to -73 -35.1 -18.9 154

7 Lw+V S -48 to -51 -0.6 160

1) P - Primary; PS - Pseudosecondary; S - Secondary

Table 2: Summary of fluid inclusion petrography and the results of microthermometric measurements. All measurements in ºC.

N Inclusion types1 XCO2 Salinity

(wt. % NaCl eq.)2

Salinity (wt. %

NaCl+CaCl2)3

Na:Ca by mass

mean range mean range mean range mean

Magnetite-(Hematite)-apatite bodies.

KR2 28 Lw+Sh+V P/PS/S ND 33.2 31.4-36.6

L4.1 28 Lw+Sh+V P/PS/S ND 36.5 33.4-41.2 41 36-46 4.1

HEN04 16 Lw+Sh(+Lc)+V P/PS/S 0.02 0.01-0.03 34.7 33.3-37.9

10 Lw+Lc+V PS/S 0.04 0.03-0.06 21.4 21.4-21.5

N1 28 Lw+Sh+V P/PS/S ND 33.3 31.5-35.3 37 34-38 2.4

N2.2 24 Lw+Sh+V P/PS/S ND 34.9 32.9-39.4 38 34-43 3.4

N2.5 21 Lw+Sh+V P/PS/S ND 35.3 31.5-38.5 38 34-43 3.7

MER2 25 Lw+nS+V PS/S ND 52.0 40.2-59.5 56 55-58 16.2

Greenstone- and Porphyry- hosted Cu mineralisation

KALL91002 15 Lw+nS+V P/PS ND 49.1 32.7-61.1 50 38-55 5.2

11 Lw+Sh+V PS/S ND 32.2 31.6-32.9

6 Lw+V PS/S ND 24.2 23.9-24.8

PAH88217 16 Lw+nS+V P/PS/S ND 53.6 46.3-57.4

PAH85117 19 Lw+nS+V P/PS/S ND 49.0 41.4-57.0

Lc+V PS/S Lc+V inclusions

P11 23 Lw+nS+V P/PS/S ND 42.0 34.1-49.1 48 44-51 14.7

K2 27 Lw+Sh+V P/PS/S ND 33.5 31.1-37.2 35 34-36 4.9

G6 22 Lw+nS+V P/PS ND 42.8 38.1-48.8 45 41-52 7.3

8 Lw+Sh+V PS/S ND 41.1 40.5-41.6

G5.1 16 Lw+nS+V P/PS ND 34.5 33.2-37.1

Lc+V PS/S Lc+V inclusions

GRUV02 14 Lw+Sh+V PS/S ND 31.3 28.9-33.3

21 Lw+V PS/S ND 16.8 10.2-23.6 16 12-22 0.4

Lc+V S Lc+V inclusions

GRUV06 28 Lw+V PS/S ND 33.1 27.1-41.2 28 24-33 0.27

Nautanen Deformation Zone(NDZ)-hosted Cu mineralisation

NAU 77006 5 Lw+Lc+V PS/S 0.18 0.17-0.20 9.1 3.7-12.4

17 Lw+Sh+V PS/S ND 34.8 31.5-41.0 36 32-43 12.3

22 Lw+V PS/S ND 19.4 12-28.3 18.6 23-23 2.4

Lc+V PS/S Lc+V inclusions

NAU 77006 18 Lw+Sh+V PS/S ND 33.2 31.3-35.0

11 Lw+Sh+V PS/S ND 28.9 27.8-29.9

Lc+V PS/S Lc+V inclusions

03NAU02 20 Lw+Sh+V PS/S ND 33.2 30.2-35.4

Lc+V PS/S Lc+V inclusions

NAU83009 30 Lw+Sh+V PS/S ND 29.3 26.2-32.3

3 Lw+Lc+V PS/S 0.23 0.19-0.29 10.3 6.7-12.9

Lc+V PS/S Lc+V inclusions

NAU05 26 Lw+Sh+V PS/S ND 43.5 31-51.8

26 Lw+V PS/S ND 27.7 21.9-32.5 25.2 22-26 0.4

9 Lc+V PS/S Lc+V inclusions

NAU09 26 Lw+Sh+V PS/S ND 33.6 32-36.5 38.7 37-42 2.5

12 Lw+V PS/S ND 24.5 21.9-26.5

A3 34 Lw+Sh+V PS/S ND 29.0 28.2-29.6

39 Lw+Lc+V S 0.1 0.05-0.29 16.0 9.7-21.1

11 Lw+V S ND 15.7 15.4-15.9

16 Lc+V S Lc+V inclusions

FERR69205 3 Lw+Sh+V PS/S ND 31.3 28.1-33.9

18 Lw+V PS/S ND 21.7 18.6-24.0

FERR69203 13 Lw+Sh+V PS/S ND 32.8 29.1-35.9 35.1 34-38 2.7

16 Lw+V PS/S ND 25.8 24.1-27.2 23.7 22-25 0.3

FERR69202 27 Lw+V S ND 21.8 19.7-25.4 19.8 19-23 0.3

7 Lw+V S ND 1.0

1) P - Primary; PS - Pseudosecondary; S - Secondary 2) Sterner et al. (1988) 3) Oakes et al. (1990)

Table 3: Summary of fluid inclusion compositions determined from microthermometry.

Detection limits (ppm)

Kiruna Fe-apatite Kiruna Cu Gruvberget Fe-oxide Cu NDZ

Sample N2.5 L4.1 KR2 HEN04 PAH 88217

K2 PAH01 KALL 91002

G6 G5.1 GRUV06 NAU09 NAU05 NAU 83009

NAU 77006

FERR 69203

Salinity 35.3 36.5 33.2 34.7 53.6 33.5 54.3 49.1 42.8 34.5 28.0 33.6 43.5 29.9 28.0 28.9

(wt. % NaCl eq.)

2 3.4 6.0 2.2 3.3 6.1 2.8 5.6 18.0 7.3 2.1 4.0 2.2 16.3 2.5 17.1 8.6

Cl 0.002 13.5 8.1 16.0 87.3 19.1 39.9 114.5 32.9 21.4 19.0 28.2 21.9 7.6 12.3 32.7 31.8

Br 0.001 0.022 0.022 0.018 0.062 BD 0.021 0.120 0.020 0.010 0.015 0.029 0.027 BD BD 0.046 0.038

Sulfate 0.001 0.101 0.110 0.093 1.740 0.001 0.649 0.860 BD 0.050 0.066 1.226 0.140 0.597 BD BD 0.002

Na 0.002 8.1 11.1 7.2 32.2 11.1 22.9 46.4 12.6 12.6 10.2 15.9 9.2 4.1 5.1 13.0 5.8

K 0.002 2.1 2.9 1.8 5.7 2.3 2.1 1.5 1.3 0.2 1.4 3.2 1.7

Li 0.002 0.016 0.012 0.016 0.062 BD 0.026 0.006 0.010 0.004 0.007

Ca 0.2 3.6 7.1 5.3 13.5 3.1 5.2 41.6 10.5 4.1 8.5 16.0 7.0 2.8 3.5 4.3 5.9

Fe 0.01 0.36 0.57 0.10 1.41 1.18 4.99 9.05 2.55 1.54 0.41 1.69 0.30 1.46 0.24 0.98 0.28

Mn 0.005 0.20 0.77 0.45 0.52 0.38 1.17 1.93 0.55 0.98 0.47 0.92 0.26 0.30 0.19 0.33 0.07

Pb 0.0001 0.07 0.07 0.07 0.14 0.02 0.09 0.09 2.11 0.09 0.78 0.04 0.02 0.02 0.06 0.01 0.01

Zn 0.001 0.14 0.28 0.27 0.24 0.08 0.25 0.35 0.10 0.13 0.08 0.09 0.14 0.21 0.07 0.13 0.05

Sr 0.001 0.14 0.20 0.27 0.33 0.07 0.32 0.46 0.10 0.10 0.14 0.18 0.08 0.05 0.06 0.09 0.12

Ba 0.001 0.70 0.72 0.85 0.60 0.22 6.28 2.61 0.25 0.17 0.17 0.34 0.07 0.35 0.07 0.14 0.05

Al 0.05 0.015 0.055 0.035 0.052 0.082 0.176 0.138 0.081 0.151 0.315 0.099 0.061 0.092 0.073 0.348 0.124

Cu 0.0001 0.006 0.013 0.011 0.031 0.006 0.072 0.069 0.012 0.504 0.616 0.157 0.014 0.172 0.009 0.067 0.028

B 0.002 0.012 0.040 0.046 0.102 0.006 0.069 0.038 0.048 0.138 0.071 0.029 0.041 0.028 0.075 0.041 0.080

Co 0.0001 0.001 0.001 0.0007 0.001 0.0008 0.005 0.003 0.005 0.002 0.002

As 0.0002 0.005 0.005 0.001 0.018 0.001 0.022 0.010 0.003 0.013 0.008 0.003 0.011 0.004 0.003

Cd 0.00001 0.001 0.001 0.001 0.001 0.0004 0.0005 0.001 0.0005 0.0002 0.0005 0.001 0.0004 0.0001 0.001 0.0001

Reconstructed fluid composition

Na 120353 100834 92202 131548 227301 110470

148134 125582

128469

78279 70638 90549 87822 67340 91126 60997

K 31150 26535 23051 23424 0 0 7351 20684 0 0 6789 13203 4498 18067 22091 17537

Li 241 106 204 252 0 0 0 0 0 0 257 125 132 28 76

Ca 53805 64746 67835 55057 63228 25288 132858 104898

42044 65232 71181 69421 59145 46365 30375 61759

Fe 5380 5201 1317 5758 24171 24090 28932 25486 15650 3131 7498 2943 31186 3091 6825 2897

Mn 3058 7027 5809 2122 7779 5670 6157 5466 9951 3653 4097 2611 6452 2539 2308 686

Pb 1076 653 909 576 422 431 282 21127 911 6027 178 192 446 729 64 95

Zn 2039 2516 3497 967 1729 1224 1130 960 1331 626 386 1336 4534 971 935 564

Sr 2138 1794 3444 1332 1377 1531 1458 953 1051 1096 820 792 1129 828 655 1266

Ba 10407 6549 10867 2438 4466 30346 8356 2453 1728 1331 1511 649 7599 905 1002 557

Al 227 499 448 214 1681 852 440 813 1542 2427 440 596 1972 960 2434 1296

Cu 92 117 145 126 128 346 220 118 5139 4749 696 136 3674 121 465 297

B 177 361 586 416 128 333 120 480 1401 548 130 407 609 982 284 839

Co 14 7 5 4 6 24 9 0 47 16 9 0 0 0 0 0

As 81 45 8 75 25 105 31 33 128 0 0 79 66 144 25 30

Cd 22 5 8 5 8 2 3 0 5 1 1 6 9 2 4 1

Cl 214087 221622 201365

210441 325232 203171

329314 298011

259705

209078

169915 203802 264179 181395

169734 175510

Br 348 602 226 149 107 345 181 121 165 175 251 239 210

Sulfate 1598 3008 1170 4194 17 3303 2474 606 725 7384 1302 20638 11

Cl/Br 615 368 889 1408 1901 954 1647 2142 1270 973 811 711 836

+ve/-ve 1.41 1.33 1.48 1.33 1.34 1.38 1.53 1.57 1.07 1.19 1.35 1.26 1.05 1.08 1.20 1.23

Table 4: Representative results of analyses of fluid inclusion leachates from vein quartz. Fluid compositions were reconstructed by charge balance of total cations against Cl molality determined from microthermometric data (Allen et al., 2005).

Site Kirunavaara Nuktus Pahtohavare Nautanen Aitik Sample KR2.4 KR2.24 KR2.17 NK2.1 NK2.3 PAH

8.14 PAH 8.20

PAH 8.9

NAU 7706e.1

NAU 7706e.2

NAU 7706t.1

A3a.1 A3.10 A3.17

Type 1 1 1 1 1 2 2 2 3 4 1 1 1 4

Salinity (wt. % NaCl eq.)

34.6 32.7 32.7 34.9 34.9 53.3 45.2 51.3 13.8 13.7 33.7 28.2 29.3 21.0

Na 110504 210340 91938 73653 184307 25816 287257 201447 54430 33245 110369 17031 189525 132340 K 72248 5720 63180 15498 20579 24209 28895 7744 Na/K 2 13 3 13 3 1 4 Ca 11682 9505 13476 17229 62346 138540 Na/Ca 9 60834 2204 21 4 2 2 Mg 28005 1 84 1392 4631 9275 51 Ba 5088 1289 1617 1227 368 95 237 1571 Mn 27598 233 5187 268 265 Fe 2373 67701 1550 129164 3612 9442 1073 960 Cu 480 252 83 2297 901 711 163 17 335 5182 Zn 761 5548 109 192 Ag 10 8337 520 487 87 bd 11 102 Au 5 58 30 6 Pb 5358 2494 805 617 160 12 266 221 B 423 31 Cl 198458 323220 Br 1961 8119

1. Lw+Sh+V; 2. Lw+nS+V; 3. Lw+V; 4. Lw+Lc+V

Table 5: Representative examples of LA-ICPMS analyses of fluid inclusions. Compositions are shown in ppm as either total cations charge

balanced against Cl molality from microthermometry (Allen et al., 2005) or normalised to Cl concentration in ppm where the major cations had

not been analysed.

KR2 N2.5 PAH88217

Crush LA-ICPMS Crush LA-ICPMS Crush LA-ICPMS

-Leach mean 30% RSD

n min max -Leach mean 30% RSD

n min max -Leach mean 30% RSD

n min max

Na 92202 89865 26960 15 44230 139972 120353 139282 41785 8 24140 195543 227301 173263 51979 22 12141 343311

K 23051 91107 27332 15 35434 130390 31150 42940 12882 8 4260 147576 31397 9419 13 4466 82450

Li 204 241

Ca 67835 10916 3275 15 2274 34627 53805 34487 10346 8 2204 160665 63228 43532 13060 13 6390 118877

Fe 1317 2068 620 15 160 6225 5380 20134 6040 8 1550 67701 24171 131303 39391 13 25850 284514

Mn 5809 3058 5120 1536 8 232 27598 7779 12011 3603 13 1063 30996

Pb 909 2779 834 6 432 5358 1076 422 843 253 5 8 2494

Zn 3497 2039 1729

Sr 3444 2138 1377

Ba 10867 4325 1298 15 348 8858 10407 3055 917 8 1289 6046 4466 2315 695 13 127 4503

Al 448 227 1681

Cu 145 558 167 13 36 3268 92 128 2266 680 9 1 2297

B 586 237 71 7 35 423 177 128 664 199 2 31 1298

Co 5 14 6

As 8 81 25

Cd 8 22 8

Cl 201365 191805 57542 7 187644 198458 214087 325232 314187 94256 4 304026 325479

Br 226 2484 745 6 186 1961 348 7609 2283 4 2967 16014

Sulfate 1170 1598 17

Table 6: Comparison of reconstructed fluid composition from crush-leach analyses with mean reconstructed fluid inclusion composition from LA-

ICPMS analyses. All concentrations in ppm.

50Km

N

Gabbro, metagabbro, diabase (<c.1.8Ga) Intrusive rocks (1.81-1.78Ga) Intrusive rocks (1.89-1.85Ga)

Svecofennian supracrustal rocks (1.96-1.85Ga) Karelian rocks (2.4-1.96Ga) Archaean rocks (>c.2.68Ga)

Allochthonous rocks (Caledonian) Major shear and deformation

zones. Fe oxide-apatite deposits Cu-(Au) deposits

Luossavaara/ Kirunavaara

Valkommen

Gruvberget

10 20 30

60 o

65 o

70 o

Sweden

Kiruna

Lule å

Stockholm

Main map

Nautanen

Pahtohavare

Kallosalmi

Mertainen

Kiskamavaara

Per Geiger Ores

Ferrum Aitik

Figure(s)

Qtz

Act

Mgt

Alb+Qtz Qtz

Ttn

Rt

Mgt

Qtz Mgt

Cpy Qtz

Ank

Cpy

Mgt Py

Cpy

Qtz

Py

Prt

Qtz

1mm

200mm

500mm 500mm

A B

C D

E F

Figure(s)

0.5mm

20mm

20mm

20mm

A B

300mm

200mm

C

D

E

F

50mm

20mm 20mm

30mm

100mm

G

I

H J

Figure(s)

Kirunavaara Luossavaara Nuktus Nuktus (deformed) Henry (Lw+Sh+V) Henry (Lw+Lc+Sh+V) Mertainen Primary Mertainen Secondary Rektorn

hydrohalite NaCl.2H2O

0

50

100

150

200

250

300

0 10 20 30 40 50 60 70

400

300

200

-10

-20

-30 -21.2

-52.2 0.0

ICE +

LIQUID

HALITE +

LIQUID

ANTARCTICITE (CaCl2.6H2O) + LIQUID

HYDROHALITE + LIQUID

wt. % NaCl eq.

100% H2O

70% NaCl 70% CaCl2

400

300

200

0

50

100

150

200

250

300

0 10 20 30 40 50 60 70 wt. % NaCl eq.

Pahtohavare Gruvberget Secondary Calcic Secondary Kallosalmi Kiskamavaara

hydrohalite NaCl.2H2O

-10

-20 -30

-21.2

-52.2 0.0

ICE +

LIQUID

HALITE +

LIQUID

ANTARCTICITE (CaCl2.6HO) +

LIQUID

HYDROHALITE + LIQUID

100% H2O

70% NaCl 70% CaCl2

400

300

200

100

-10

-20 -30

-21.2

-52.2

0.0

hydrohalite

NaCl.2H2O

ICE +

LIQUID

HALITE

+ LIQUID

ANTARCTICITE

(CaCl2.6H2O) +

LIQUID

HYDROHALITE +

LIQUID

0

50

100

150

200

250

300

350

0 10 20 30 40 50 60

wt. % NaCl eq.

100% HO 2

70% NaCl 70% CaCl2

Aitik Lw+Lc+V Lw+Sh+V Lw+V

Nautanen Lw+Lc+V Lw+Sh+V Lw+V

Ferrum Lw+Sh+V Lw+V Lw+V (calcic)

T hL-

V (

°C)

T hL-

V (

°C)

T hL-

V (

°C)

A

B

C

Figure(s)

Ferrum

Aitik

0

50

100

150

200

250

300

350

400

450

500

0 100 200 300 400 500 600

Lw+Sh+V Lc+V

Th to Lc

Lw+Lc+V

21.0 wt % NaCl eq

XCO2=0.04

Lw+Lc+V

8.5 wt % NaCl eq

XCO2=0.08

Lw+Lc+V

19.7wt % NaCl eq

XCO2=0.3

Lc+V

Th to V

T ( C)

P (

MP

a)

0

100

200

300

400

500

600

0 100 200 300 400 500 600

Lc+V

Th to Lc

Lw+Lc+V

6.7 wt % NaCl eq

XCO2=0.22

Lw+Lc+V

12.9 wt % NaCl eq

XCO2=0.21

Lw+Lc+V

10.9 wt % NaCl eq

XCO2=0.16

Lw+Lc+V

6.5wt % NaCl eq

XCO2=0.19

Lw+V

13.0 wt % NaCl+CaCl2

Th=172

Lw+V

19.0 wt % NaCl+CaCl2

Th=144

Lw+V

26.0 wt % NaCl+CaCl2

Th=134

T ( C)

P (

MP

a)

A

B

Calcic

22.5 wt. %

NaCl+CaCl2 eq.

NaCl/CaCl2=0.36

Th=131 C Calcic

19.0 wt. %

NaCl+CaCl2 eq.

NaCl/CaCl2=0.30

Th=153 C

0

100

200

300

400

500

600

0 100 200 300 400 500 600 T ( C)

P (

MP

a)

Th L

-V (

°C)

Th L

-V (

°C) 50

100 150 200 250 300 P (Mpa)

50

100

150

200

250

300

350

400

50 100 150 200 250 300 350 400 450 500 Tsol Halite (°C)

Magnetite-apatite deposits

Kirunavaara Luossavaara Nuktus Nuktus (deformed) Henry (Lw+Sh+V) Mertainen Primary Mertainen Secondary Rektorn

50 100

200 250 300 P (Mpa)

50

100

150

200

250

300

350

400

50 100 150 200 250 300 350 400 450 500 Tsol Halite (°C)

IOCG deposits

150

Pahtohavare Kallosalmi Kiskamavaara Gruvberget

Deformed (NDZ) Cu-Au

deposits

50 100

200 250 300 P (Mpa)

50

100

150

200

250

300

350

400

50 100 150 200 250 300 350 400 450 500 Tsol Halite (°C)

Th L

-V (

°C)

150

Aitik Nautanen Ferrum

A B

C D

E F

Figure(s)

Seawater

Halite dissolution/ Cl-enriched sources

Bittern brines

Log Br (ppm)

Lo

g C

l (p

pm

)

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

0 2000 4000 6000 8000 10000 12000

Cl/Br (molal)

Na/B

r (m

ola

l)

Seawater

0

2000

4000

6000

8000

10000

12000

0 10 20 30 40 50 60

Salinity (wt. % NaCl eq.)

Cl/

Br

(mo

lal)

Seawater ‘Magmatic’

Se

aw

ate

r

1:1

1) Bohlke and Irwin, 1992 2) Kendrick et al, 2001

3) Johnson et al, 2000

Se

aw

ate

r

Porphyry fluids

Mantle

Fumaroles

‘Magmatic’

Na-Ca exchange - albitisation/ scapolitisation

3.5

4.0

4.5

5.0

5.5

6.0

6.5

7.0

7.5

1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0

Kiruna - type CL

Kiruna district IOCG CL

Gruvberget CL

Nautanen CL

Ferrum CL

A

B

C

Figure(s)

Na

Ca K

Na

Ca K

Na

Ca K

Kiruna (Laser Ablation) Nuktus (Laser Ablation) Kiruna type (Crush leach)

Pahtohavare (Laser ablation) IOCGs (Crush Leach) Gruvberget (Crush Leach)

Nautanen (Laser Ablation) Lw+V Lw+Lc+V Lw+Sh+V Aitik (Laser ablation) Lw+Sh+V Nautanen (Crush Leach) Ferrum (Crush Leach)

IOCGs

Gruvberget Ca-rich secondaries

A

B

C

Figure(s)

1

10

102

103

104

105

106 F

e (

pp

m)

10-2 10-1 1 10 102 103

Fe/Mn

1

10

102

103

104

Cu

(p

pm

)

10-2 10-1 1 10 102 103

Fe/Mn

B

Kiruna-type IOCG NDZ (crush leach) NDZ Lw+v NDZ Lw+Sh+V NDZ Lw+Lc+V

CL LA-ICPMS

A

Figure(s)

1

10

102

103

104

105

0.0 10.0 20.0 30.0 40.0 50.0 60.0

Salinity (weight % NaCl eq.)

Cu

(p

pm

)

1

10

103

104

105

Fe (

pp

m)

102

106

0.0 10.0 20.0 30.0 40.0 50.0 60.0

Salinity (weight % NaCl eq.)

0.0 10.0 20.0 30.0 40.0 50.0 60.0 Salinity (weight % NaCl eq.)

Zn

(p

pm

)

0.0 10.0 20.0 30.0 40.0 50.0 60.0

Salinity (wt. % NaCl eq.)

1

10

102

103

104

105

Pb

(p

pm

)

0.0 10.0 20.0 30.0 40.0 50.0 60.0

Salinity (weight % NaCl eq.)

1

10

102

Au

(p

pm

)

0.0 10.0 20.0 30.0 40.0 50.0 60.0

Salinity (weight % NaCl eq.)

1

10

102

103

104

105

Ag

(p

pm

)

Kiruna-type IOCG NDZ (crush leach) NDZ Lw+v NDZ Lw+Sh+V NDZ Lw+Lc+V

CL LA-ICPMS

1

10

103

104

105

102

106

A B

C D

E F

Figure(s)

-4.5

-4.0

-3.5

-3.0

-2.5

-2.0

-1.5

-1.0

-0.5

0.0

0 0.0005 0.001 0.0015 0.002 0.0025 0.003

1

10

102

103

104

105

0 50 100 150 200 250 300 350 400 450 500 Temperature (fluid inclusion Th °C)

Cu

(p

pm

)

1

10

102

103

104

105

0 50 100 150 200 250 300 350 400 450 500 Temperature (fluid inclusion Th °C)

Fe (

pp

m)

106

1

10

102

103

104

105

0 50 100 150 200 250 300 350 400 450 500 Temperature (fluid inclusion Th °C)

Pb

(p

pm

)

1/T (K-1)

Lo

g (

mo

lal F

e/C

l)

-12.0

-10.0

-8.0

-6.0

-4.0

-2.0

0.0

Lo

g (

mo

lal C

u/C

l)

0 0.0005 0.001 0.0015 0.002 0.0025 0.003 1/T (K-1)

-12.0

-10.0

-8.0

-6.0

-4.0

-2.0

0.0

Lo

g (

mo

lal P

b/C

l)

0 0.0005 0.001 0.0015 0.002 0.0025 0.003 1/T (K-1)

Kiruna-type IOCG NDZ (crush leach) NDZ Lw+v NDZ Lw+Sh+V NDZ Lw+Lc+V

CL LA-ICPMS

A B

C D

E F

Figure(s)

102

103

104

0 5000 10000 15000 20000 25000 30000 SO4 (ppm)

Cu

(p

pm

)

102

103

104

105

0 5000 10000 15000 20000 25000 30000 SO4 (ppm)

Fe (

pp

m)

102

103

104

0 5000 10000 15000 20000 25000 30000

Zn

(p

pm

)

SO4 (ppm)

102

103

104

105

0 5000 10000 15000 20000 25000 30000

SO4 (ppm)

Pb

(p

pm

)

Kiruna type IOCG Gruveberget Nautanen Ferrum

A B

C D

Figure(s)